Since monoclonal antibodies have been useful for the examination of antigenic and functional properties of several influenza virus proteins, we have utilized a similar approach to the study of influenza matrix and polymerase proteins. We generated five monoclonal antibodies that inhibit the in vitro RNA transcriptase activity of influenza virus and bind to a protein which co-migrates with the influenza polymerase proteins in acrylamide gels. Preliminary results indicate that these antibodies are directed at the polymerase enzyme(s) of influenza virus, but additional study is necessary to conclusively demonstrate their specificities. Six monoclonal antibodies to the matrix protein are also under investigation. Preliminary results indicate that little antigenic variation occurs in the influenza virus matrix protein.